I don't mind anyone being passionate in some belief, be it religon, meat, politics, whatever. Doesn't bother me at all. What bothers me is when someone tries to ram a message down your throat. Then I have a problem with it. If you are a vegan, good for you. If you want to stand outside the butchers protesting, knock yourself out.
But no one has the right to hurl insults or even get violent or obstructive. If that happens whatever noble message you may have been trying to sell is sarcificed. That goes for anything, not just vegans. I am not an especially big meat eater either! I wouldn't stand for it, not for a nano second.